Joint Relay Selection and Power Allocation in Large-Scale MIMO Systems with Untrusted Relays and Passive Eavesdroppers

摘要

In this paper, a joint relay selection and power allocation (JRP) scheme isproposed to enhance the physical layer security of a cooperative network, wherea multiple antennas source communicates with a single-antenna destination inpresence of untrusted relays and passive eavesdroppers (Eves). The objective isto protect the data confidentially while concurrently relying on the untrustedrelays as potential Eves to improve both the security and reliability of thenetwork. To realize this objective, we consider cooperative jamming performedby the destination while JRP scheme is implemented. With the aim of maximizingthe instantaneous secrecy rate, we derive a new closed-form solution for theoptimal power allocation and propose a simple relay selection criterion undertwo scenarios of non-colluding Eves (NCE) and colluding Eves (CE). For theproposed scheme, a new closed-form expression is derived for the ergodicsecrecy rate (ESR) and the secrecy outage probability as security metrics, anda new closed-form expression is presented for the average symbol error rate(SER) as a reliability measure over Rayleigh fading channels. We furtherexplicitly characterize the high signal-to-noise ratio slope and power offsetof the ESR to highlight the impacts of system parameters on the ESR. Inaddition, we examine the diversity order of the proposed scheme to reveal theachievable secrecy performance advantage. Finally, the secrecy and reliabilitydiversity-multiplexing tradeoff of the optimized network are provided.Numerical results highlight that the ESR performance of the proposed JRP schemefor NCE and CE cases is increased with respect to the number of untrustworthyrelays.